Axial flow combine

ABSTRACT

A combine for harvesting and threshing grain has features to prevent grain and time wastage even if the combine is tilted sideways, and other features to simplify the threshing equipment. The combine has a sieve housing that is mounted on rollers to the frame. These rollers allow the sieve housing to swing like a pendulum if the combine tilts sideways. The combine has inner and outer cylindrical bodies that rotate together opposite to the rotation of a threshing drum. The threshing drum and grate are conical with the rearward end being smaller than the forward end. A beater for beating grain rotates with the threshing drum, causing grain to fall through slots located in the inner body. The space between the inner and outer body contains a helical flight for transporting this rescued grain back to the forward end and to the sieves. Elevating rings mounted to the outer body rotate with the outer body to lift material from the sieve to the bin, if clean grain, and back to the threshing grate, if tailings.

BACKGROUND OF THE INVENTION

This invention relates in general to agricultural equipment and inparticular to a combine for harvesting and threshing grain using anaxial flow threshing and separating means.

Self-propelled combines for harvesting and threshing grain such as wheathave been available for many years. These combines are large deviceshaving a frame mounted on wheels. A header, often 14 to 30 feet wide,cuts the crop and forces it inwardly into a threshing means. Thethreshing means includes a cylinder with protruberances such as raspbars that are rotated closely past a grate. The feed may be tangentialor axial into the cylinder. Some of the cylinders are flared or conical.Grain threshed from the crop is conveyed into a sieve means whichnormally has primary and secondary sieves for removing chaff andreturning tailings. The sieves are screens with inclined fingers, thescreens being shaken to cause the clean grain to fall through. A blowerblows air across the sieves to discharge the chaff. Tailings, which aretoo heavy to be blown out, but too large to fall through the fingers,are returned for further threshing to remove the grain from the debrisof the crop.

After threshing, the crop debris, such as the straw, is pushed out byvarious means and discharged. The clean grain from the sieve is conveyedup to a storage bin on top of the combine, normally by paddles mountedon a chain. When the bin is full, the grain is conveyed into a truck ortrailer by means of an auger connected to the bin.

While successful, the large nuaber of moving parts makes these combinesexpensive. The complexity also makes the combines subject to frequentfailure. There are many bearings, V-belts, pulleys, chains and the like.Another problem occurs when the combine tilts transversely or sidewayson a hill. This tends to load up one side of the sieves. Unless theoperator slows the machine, grain is likely to be blown out and wasted.Slowing down the machine might avoid wastage of grain, but results inlower productivity for the combine. Combines with means for levelingportions of the combine to avoid this problem are available. However,the hydraulic systems used are complex and expensive.

SUMMARY OF THE INVENTION

A combine is provided with this invention that has many new features toreduce the complexity and accommodate for transverse tilting of thecombine. To handle the tilting, the sieve housing is mounted on rollerswhich are carried in curved guide tracks. These rollers allow the sievehousing to swing with respect to the frame under the action of gravityand to remain level even when the combine becomes tilted.

The threshing and separating is handled by an axial flow assembly thatextends longitudinally parallel with the longitudinal axis of the frame.This assembly includes a conical threshing drum with its large end atthe intake. The conical threshing drum rotates within a conicalthreshing grate, which has bars that allow threshed grain to fallthrough into the sieve assembly. The threshing grate is connected to anouter body that rotates in the opposite direction to the rotation of thedrum. An inner body is located inside the outer body, both of thesebodies being cylindrical and concentric. The inner body is perforatedfor allowing grain to pass through into an area between the inner andouter bodies. A beater connected with the thresher drum beats the cropmaterial after being threshed to further separate any grain and cause itto fall through the perforated inner body. The inner and outer bodiesrotate together, and a helical flight is located between the bodies tocause the separated grain to move forwardly to the sieve. An innerhelical flight located on the inner side of the inner body urges strawout the rearward end of the inner body.

A pair of elevating rings extend circumferentially around the outer bodyand rotate with the outer body. These elevating rings have individualcompartments which will pick up material at a lower level and dump it ata higher level. The inner elevating ring picks up tailings dischargedfrom the sieve and returns it to a tailing intake, which delivers thematerial back to the threshing drum. The outer elevating ring picks upclean grain and delivers it upwardly to a storage bin intake.

A rack and pinion assembly mounted to the rear of the thresher andbeater assembly allows the clearance between the thresher drum andconical grate to be varied by rotating the pinion. All of the variousrotating members are driven by engagements of the rotating members.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view, partially simplified, of a confineconstructed in accordance with this invention.

FIG. 2 is a partial perspective view of the combine of FIG. 1, withportions broken away.

FIG. 3 is a sectional view of the combine of FIG. 1, taken along theline III--III of FIG. 1.

FIG. 4 is a sectional view of the combine of FIG. 1, taken along theline IV--IV of FIG. 3.

FIG. 5 is a partial perspective view looking inward into the clean grainelevating ring.

FIG. 6 is an exploded perspective view of the threshing and separatingmeans of the combine of FIG. 1.

FIG. 7 is an enlarged sectional view of the rack and pinion assembly foradjusting the thresher drum of the combine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, combine 11 has a frame 13 comprised mainly ofsquare tubular members. Wheels 15 are mounted to the frame, and anengine 17 drives the forward wheels as well as supplies power for thethreshing functions. A conventional header assembly 19 is mounted to theforward end of frame 13. Header assembly 19 has a blade (not shown) thatis reciprocated past knives (not shown) for cutting the crop. An auger(not shown) delivers the crop to the center, which is then conveyedupward on a chain belt (not shown). The operator controls the combinewithin a cab 21. Clean grain is stored in a bin 23 for subsequentunloading by an auger (not shown).

Combine 11 includes an outer body 25 that is generally cylindrical, hasa longitudinal axis that is parallel with the longitudinal axis of theframe, and extends much of the length of frame 13. Outer body 25 isrotated at a fairly low speed, about 20 revolutions per minute, by meansof a pulley 27, which engages a V-belt 29. Belt 29 is driven by a drivepulley 31 connected to engine 17. As shown in FIG. 2, frame 13 has anupright cradle 32 that supports two rollers 33. The rollers 33 engageand support the outer body 25 to allow it to rotate. Similar rollers(not shown) are mounted on a cradle at the rearward end of frame 13.

Referring still to FIG. 2, the portion of the outer body 25 that isengaged by rollers 43 is a cylindrical feeder housing 35. Feeder housing35 is formed separately from outer body 25 and bolted as shown in FIG.6. A circular, stationary plate 37 fits within the front opening offeeder housing 35. Plate 37 is rigidly mounted to frame 13 and has abracket 39 for receiving the header 19 (FIG. 1). Crop from the header 19passes through an aperture 41 provided in stationary plate 37. As shownin FIG. 1, wheels 43 are mounted on the inside of stationary plate 37for engaging the inner wall of feeder housing 35. Wheels 43 support thestationary plate 37 and are centered and adjusted by means of bolts thatextend through slots 44 (FIG. 2).

Referring again to FIG. 1, a longitudinal axle 45 extends through andpast the outer body 25. Axle 45 is carried in a bearing 47 on theforward end, which is mounted to stationary plate 37. The rearward endof axle 45 is supported in a frame member 49 that is secured to outerbody 25 for rotation in unison. A multiple member drive linkage 51extends from drive pulley 31 to the rearward end of axle 45 for rotatingaxle 45 in a direction that is opposite to the rotation of outer body25. Linkage 51 is geared so as to provide axle 45 with a considerablyhigher speed of rotation than outer body 25, such as about 600revolutions per minute. A conventional straw spreader 52 is secured to avertical member of the drive linkage 51.

Referring to FIG. 1 and FIG. 6, threshing is handled by a threshing drum53. A feeder head 54 is formed on the forward portion of drum 53. Feederhead 54 is frusto-conical with its smaller end on the forward end.Feeder head 54 contains impellers 55 for grabbing the crop in the feederhousing 35 and forcing it rearwardly. Helical flights 56 (FIG. 6)located on the inner wall of feeder housing 35 also urge the croprearwardly. Threshing drum 53 is also frusto-conical, however, itslarger end is located forwardly of the rearward end and joins the feederhead 54. Threshing drum 53 converges to a smaller diameter rearwardlyand has rasp bars 57 spaced on this converging sidewall surface forperforming the threshing. Rasp bars 57 have protruberances and areinclined or spiraled into the direction of rotation to push the croprearwardly.

The rasp bars 57 rotate in close proxiaity to a threshing grate 59.Grate 59 has a mating frusto-conical sidewall comprised of a pluralityof bars extending 360 degrees around the grate, each spaced apart todefine slots for threshed grain to fall through. Grate 59 thus convergesto a smaller diameter in a rearward direction. Grate 59 is rigidlymounted to outer body 25 for rotation therewith. As a result, in thethreshing space located between threshing drum 53 and grate 59, raspbars 57 will be rotating in one direction while grate 59 rotates in theoppposite direction. Openings 60 are provided in outer body 25 for grainto pass after threshing.

Grate 59 is also rigidly connected to an inner body 61 for rotation inunison. Inner body 61 is a cylindrical member having a concentric axiswith outer body 25 but of a lesser diameter. This defines a cylindricalspace between the inner body 61 and the outer body 25. Inner body 61 isperforated its entire length and circumference with slots 63. Slots 63allow any grain that is separated in the inner body to pass through intothe space between the inner body 61 and outer body 25. An outer flight65 is rigidly connected between the inner and outer bodies and spiraledalong their lengths. The direction of the spiraling of flight 65 is suchthat material falling into the spaces between the flights 65 will bemoved forwardly as the inner body 61, outer body 25 and outer flight 65rotate in unison. This causes any grain located in this space to bedrawn to the forward end of the combine for further handling.

Crop debris from the threshing drum 53 is pushed into the inside ofinner body 61. An inner flight 67 located on the inner wall of innerbody 61 is spiraled opposite to outer flight 65 to push this cropmaterial in a rearward direction, where it exits and is spread by thestraw spreader 52. A beater 69 is rigidly mounted to the rearward end ofthreshing drum 53 for beating the crop material forced into the innerbody 61 to remove any grain that may not have been threshed by thethreshing drum 53. Beater 69 extends the length of inner body 61 and istriangular in cross-section as shown in FIGS. 3 and 6. The periphery ofbeater 69 is closely spaced to the inner flight 67.

Beater 69, as shown in FIG. 3, includes a cylinder 70 with threetriangular ribs 72. Each rib 72 is secured to cylinder 70 and extendsradially outward. Each rib 72 is parallel to the other ribs 72 andextends the full length of cylinder 70.

Referring to FIGS. 1, 2 and 3, a sieve housing 71 is suspended belowouter body 25. Sieve housing 71 is supported by forward or fore rollers71 (FIGS. 1 and 2) that are carried in a guide track 75. Guide track 75is a circular track that is mounted to the feeder housing 35 section ofthe outer body 25. Guide track 75 extends around the circumference ofthe feeder housing 35. Aft rollers 77 on the rearward end are located ina guide track 79 that extends circumferentially around the outer body25. Both guide tracks 75 and 79 rotate in unison with the outer body 25.The rollers 73 and 77, however, allow the sieve housing 71 to remainstationary. Rollers 73 and 77 also allow the sieve housing 71 to remainlevel or in the same transverse plane even though the frame 13 tiltstransversely or sideways. The action of gravity will cause this levelingor pendulum effect.

A shock absorber 80, shown in FIG. 2, prevents too much swinging motionby providing dampening in a rotational direction. Shock absorber 80 isconnected between a portion of frame 13 and sieve housing 71. Also shownin FIG. 2 is a cover 82 that extends from the top of each side of sievehousing 71. Cover 82 is an arcuate member that covers the openings 60 inouter body 25 provided to allow grain to fall from the grate 59 into thesieve housing 71. Cover 82 covers only the openings 60 when they arerotated onto the upper side.

Referring to FIGS. 1 and 3, the sieve means includes a spreader 81located immediately below openings 60. Spreader 81 is located in aV-shaped trough 83 for distributing grain falling from grate 59 alongthe length of sieve housing 71. Spreader 81 is driven by a roller (notshown) that is frictionally driven through contact with guide track 75(FIG. 1). A primary sieve 85 of a conventional nature is locatedimmediately below spreader 81. Sieve 85 has rows of inclined, serratedchaffer fingers. Half of the rows of primary sieve 85 incline to theright, and the other half incline to the left. The inclination of therows of fingers can be adjusted to vary the openings of the primarysieve 85.

A secondary sieve 87 of the same structure as primary sieve 85 islocated below the primary sieve 85. Both sieves 85 and 87 are shaken orreciprocated by shaker means that includes eccentric wheels 89. Thesewheels 89 oscillate the sieves 85 and 87 in a slightly up and down andlateral direction. The lateral movement causes material on the sieves totend to move to the right and left sides of the sieve housing 71. Theeccentric wheels 89 are timed so as to shake the sieves 85 and 87 out ofsequence with each other.

A blower 91 is mounted on the bottom of sieve housing 71. Blower 91discharges air upwardly through a slot 93 that extends the length ofsieve housing 71. This air discharges through the sieves 85 and 87,which deflect the stream of air outwardly in right and left directions.Clean grain that falls through the apertures in sieves 85 and 87 fallsonto one of two bottom sloping portions 95 of sieve housing 71. Eachsloping portion 95 slopes opposite to the other laterally downward to acorner with a sidewall 97. Each sidewall 97 is a vertical wall with awindow 99 on its upper section for allowing air from blower 91 todischarge. Chaff separated from the grain will also be blown out thewindows 99. The clean grain will gravitate to one of the corners of asloping portion 95 with a sidewall 97, where an auger 101 will transportthe clean grain rearwardly for collection. The material which is toolarge to pass through the sieves 85 and 87, and too heavy to be blownfrom the primary sieve 85 will likely have grain firmly embedded withincrop debris. This material, called tailings, is discharged into achannel 103 mounted to each sidewall 97 below window 99. A tailingsauger 105 in channel 103 transports the trailings rearwardly forrecycling.

A pair of elevating rings 107 and 109 are mounted in the same verticalplane and concentric with guide track 79. Elevating rings 107 and 109and guide track 79 are all rigidly mounted to a plate or wall 113 (FIG.4), which is rigidly mounted to outer body 25. The clean grain auger 101is driven by frictional engagement with elevating rings 107, which isthe larger diameter elevating ring. The clean grain auger 101 dischargesclean grain into compartments formed in elevating ring 107. Thetrailings auger 105 similarly is driven by engagement with the lesserdiameter elevating ring 109. The tailings are distributed intocompartments formed in elevating ring 109.

Referring to FIG. 4, each compartment consists of an outer diameter orouter wall 111, which is a cylinder concentric with the axle 45 (FIG.1). Outer wall 111 extends between rearward wall 113 and a forward wall115. Rearward wall 113 is a plate that extends from the outer body 25 tothe outer wall 111 of the outermost elevating ring 107. The forward wall115 is parallel to the rearward wall 113, but is an annular plate thatextends only the transverse width of an elevating ring 107 or 109.Radial partitions 117 are spaced along the elevating rings 107 and 108,each partition extending from the outer wall 111 and between the forwardwall 115 and rearward wall 113.

The compartment means is completed by a lower cover plate 119 and anupper cover plate 121. Cover plates 119 and 121 are located on the righthalf of the elevating rings 107 and 109, when viewed as shown in FIG. 3,to prevent grain from falling out, the direction of rotation beingcounterclockwise. The compartments of the elevating rings 107 and 109 onthe left half will be empty until reaching the left tailings auger 105and clean grain auger 101, and thus do not need a cover plate. The lowercover plate 119 is rigidly secured to sieve housing 71 for movementtherewith. The upper cover plate 121 is rigidly secured to bin 23. Sincesieve housing 71 will swing or rotate with respect to bin 23 whencombine 11 tilts sideways, the cover plates 119 and 121 telescope oroverlap. Cover plates 119 and 121 thus do not rotate with the elevatingrings 107 and 109.

Each cover plate, as shown in FIG. 4, has an elastomeric liner 123 thatextends substantially the width of the outer wall 111. Liner 123 islocated on the inner side of partitions 117 and in sliding engagementwith a guide track 125. Rollers 127 rotate in the guide track 125, whichhas both inner and outer walls. Rollers 127 are spaced apartcircumferentially and mounted on axles 129. Each axle extends through abracket 131 that is secured to the elastomeric liner 123.

Referring to FIG. 2, the upper cover plates 121 terminate at a binintake 133. Elevating ring 107 registers with an upper portion of binintake 133 for discharging grain into an auger 135. Auger 135 conveysthe grain into bin 23. The lower portion of bin intake 133 is verticallydivided from the upper portion and comprises a tailings intake forreceiving tailings from elevating ring 109. A tailings return auger 137extends across bin 23 to a tailings return conduit 139. Conduit 139delivers tailings back to the feeder housing 35 for rethreshing. A chaindrive 141 is secured to one of the wheels 43 (FIG. 1) for drivingtailings auger 137. A chain drive 143 extending from the rearward end oftailings auger 137 drives the clean grain auger 135.

Referring to FIG. 1, the clearance between the threshing drum 53 andgrate 59 can be varied by advancing axle 45 in a forward or rearwarddirection. This is handled by a rack and pinion assembly 145 mountedbetween frame member 49 and axle 45. One embodiment of the rack andpinion means 145 is shown in FIG. 7. This embodiment includes a pinion147 rotatably mounted to frame member 49. The pinion 147 is a circulargear having teeth that engage teeth of a straight rack 149. Screws 151connect rack 149 to a member 153. Member 153 is carried between twoflanges 155 and 157. Upper and lower guide rods 159 extend between theflanges 155 and 157 and through holes formed in frame member 49. Eachflange 155 and 157 receives a set of roller bearings 161. Each bearing161 has a sleeve 163 located on its inner side that is keyed to axle 45by means of a key 165. Axle 45 has a shoulder 167 that faces rearwardlyand is located on the forward side of frame member 49. A collar 169 isbolted to the axle 45 on the rearward side of flange 157.

In the operation of the rack and pinion means of FIG. 7, rotating pinion147 causes translational movement of rack 149, and along with it flanges155 and 157. Flanges 155 will bear against shoulder 167 to move axle 45forwardly if forward direction is desired to provide more threshingclearance. If rearward direction is desired, rotation of pinion 147 inthe opposite direction will cause flange 157 to bear against collar 169to move axle 45 in the rearward direction.

In the overall operation of combine 11, header 19 will cut the grain andtransport it into the feeder housing 35. Impellers 55 will draw thegrain inwardly into the threshing area between threshing drum 53 andgrate 59. Much of the grain will be separated at this point and fallthrough the slots in grate 59 into the spreader 81 of the sieve means.The remaining portion of the crop will be forced into the inner body 61,which is rotated in a direction opposite to the rotation of thethreshing drum 53. The beater 69 will beat the crop material, forcingany remaining grain out, to fall through the slots 63 in the inner body61. The inner flight 67 will push the debris rearwardly to discharge andbe spread by the spreader 52.

The rescued grain falls into an annular space between the inner body 61and outer body 25. The outer flight 65 moves the rescued grain forwardlydue to the rotation of the inner and outer bodies together. This rescuedgrain, along with initially threshed grain falls onto the spreader 81,which spreads the grain over the primary sieve 85. Clean grain fallsthrough the primary sieve 85 and secondary sieve 87 to the bottom of thesieve housing 71. Chaff is blown laterally outward through windows 99 bythe blower 91. Tailings are distributed into a tailings channel 105(FIG. 3) for rethreshing. Clean grain is delivered to the rear of thesieve housing by auger 101 (FIG. 3) for transmission to the storage bin23.

The outer elevating ring 107 receives the clean grain from the cleangrain auger 101 and delivers it upwardly to storage bin 23. The innerelevating ring 109 receives tailings from the auger 105 and delivers itup to an auger 137. Auger 137 delivers the tailings to conduit 139 forconveying back to the feeder housing 35.

The invention has significant advantages. The pendulum mounting of thesieve housing allows it to remain level in a transverse direction eventhough the frame of the combine tilts sideways. This allows one tomaintain a high speed of cutting when tilted, without risking loss ofgrain being blown out along with chaff. The elevating rings allow thepickup of material from the sieve and delivery for storage or recyclingregardless of the location of the sieve with respect to the frame. The360 degree, rearwardly converging threshing grate and the counterrotation of the grate with the threshing drum, cause threshing in ashorter distance, with less pressure and with less power requirementsthan conventionally. Rotation of the various members through rollers,which can be elastomeric, reduces vibration over previous machines whichused an extensive amount of belts and chains.

While the invention has been shown in only one of its forms, it shouldbe apparent to those skilled in the art that it is not so limited but issusceptible to various changes without departing from the spirit of theinvention.

I claim:
 1. In a combine having a frame mounted on wheels and having alongitudinal axis, threshing means carried by the frame for receivingcrop and threshing grain from the crop, the improvement comprising incombination:a sieve housing, carried below the threshing means, having abottom with a sloping portion that slopes transverse to the longitudinalaxis, a sidewall with a window, and a channel mounted to the inner sideof the sidewall below the window; primary and secondary sieves mountedin the housing and vertically spaced apart; shaker means for shaking thesieves to facilitate the passage of clean grain through the sieves tothe sloping portion and tailings to the channel for return to thethreshing means; a blower mounted below the housing for blowing airupwardly through the sieves to discharge chaff through the window; andthe housing being carried by fore and aft rollers rotatably mounted tothe housing and longitudinally spaced apart, the rollers being carriedin curved guide tracks carried by the frame.
 2. The combine according toclaim 1 wherein thebottom of the housing has a longitudinal slot forreceiving air discharged from the blower.
 3. The combine according toclaim 1 wherein a tailings auger is located in the channel for movingtailings to one end of the housing for returning to the threshing means.4. The combine according to claim 1 wherein a clean grain auger islocated at the intersection of the sloping portion and the sidewall formoving the clean grain to one end of the housing for collection.
 5. Thecombine according to claim 1 wherein each of the sieves has a pluralityof fingers located in longitudinal rows, the fingers pointing toward thewindow.
 6. The combine according to claim 1 wherein the housing has twoof the sidewalls, each having a window, two of the sloping portions,each inclined downwardly to one of the sidewalls, and two of thechannels, each mounted to one of the sidewalls.
 7. The combine accordingto claim 1 further comprising:a spreader mounted between the threshingmeans and the primary sieve for distributing grain from the threshingmeans onto the primary sieve.
 8. The combine according to claim 7wherein the spreader comprises:a rotatably driven member mounted todefine a circular path in and transverse to a stream of grain fallingfrom the threshing means.
 9. In a combine having a frame mounted onwheels, threshing means for removing grain from crop and passing thegrain to sieves for separating chaff from the grain, an improvedconveyor for transporting grain from the sieves to a storage bin mountedon the frame, comprising:a rigid, circular, elevating ring mounted tothe frame and rotatably driven past a discharge of the sieves and anintake of the bin, the elevating ring having a plurality of compartmentsfor receiving grain discharged from the sieves and dumping the graininto the bin intake.
 10. The combine according to claim 9 wherein thecompartments comprise:spaced apart partitions mounted rigidly to thering each having an outer wall and forward and rearward walls, thecompartments further having a cover plate carried by the frame to allowrotation of the rings with respect to the cover plate, the cover platebeing closely spaced to the elevating ring to define an inner wall asthe partitions rotate past.
 11. In a combine having a frame mounted onwheels, threshing means for removing grain from crop and passing thegrain to sieves for separating chaff from the grain and returningtailings to the threshing means, an improved conveyor for transportinggrain from the sieves to a storage bin mounted on the frame,comprising:a pair of rigid, circular elevating rings mounted forrotation in unison past the sieves and the bin, the rings having aplurality of compartments for receiving granular material at a lowerlevel and dumping the material at a higher level, one of the ringsregistering with a clean grain discharge from the sieves and with a binintake, the other of the rings registering with a tailings dischargefrom the sieves and a tailings return intake.
 12. The combine accordingto claim 11 wherein each of the rings is mounted in a plane that isnormal to a longitudinal axis of the frame.
 13. A combine having a framemounted on wheels and comprising in combination:a pair of rigid,circular elevating rings rotatably carried by the frame; each of therings having a plurality of compartments for receiving grain at a lowerlevel and dumping the grain at a higher level; threshing means carriedby the frame for removing grain from crop; and sieves mounted below thethreshing means for receiving grain from the threshing means and fordischarging chaff separated from the grain received, and for deliveringclean grain to two clean grain discharges, and tailings to two tailingsdischarges; one of the clean grain discharges and one of the trailingsdischarges being located on each side of the sieves; one of the ringsregistering with each of the clean grain discharges and a storage binintake for receiving clean grain and transporting it to the bin intake,the other of the rings registering with each of the tailings dischargesand a tailings return intake, for returning tailings to the threshingmeans.
 14. The combine according to claim 13 wherein the sieves aremounted in a housing that is supported from the frame by four rollers,two on each side of the sieves for allowing the housing to remain levelwhen the frame tilts sideways.
 15. The combine according to claim 14wherein the compartments comprise:forward, rearward, and outer wallsmounted to each of the rings for rotation therewith; a plurality ofspaced apart partitions radially mounted to the rings and connecting theforward and rearward walls; a pair of lower, curved cover plates, eachmounted stationarily to the sieve housing on one side and extendingumwardly along the inner diameter of each of the rings to define innerwalls of the compartments as the partitions rotate past; and a pair ofupper, curved, cover plates, each carried stationarily by the frame andextending downwardly on one side of the frame along the inner diameterof each of the rings to define inner walls of the compartments as thepartitions rotate past, the upper and lower cover plates overlapping toaccommodate movement of the sieve housing with respect to the frame. 16.In a combine having a frame with a longitudinal axis and threshing meanscarried by the frame for receiving crop and threshing grain from thecrop, the improvement comprising in combination:a sieve housing carriedbelow the threshing means, having a bottom with two sloping portionsthat slope transverse to the longitudinal axis of the frame, eachinclining in opposite directions downwardly to an upright sidewall; eachsidewall having a window with a channel mounted to the inner side of thesidewall below the window; primary and secondary sieves mounted in thehousing and vertically spaced apart, each of the sieves having aplurality of fingers located in longitudinal rows, half of the fingersin each sieve pointing toward one of the windows and half pointingtoward the other of the windows; shaker means for shaking the sievestransverse to the longitudinal axis of the frame to facilitate thepassage of grain through the sieves to the sloping portions, andtailings to the channels for return to the threshing means; and blowermeans for blowing air upwardly through the sieves to discharge chaffthrough the windows.